1. Field of the Invention
This invention lies in the field of ratchet action open ended spanners for use in tightening and loosening bolt heads and nuts, for example, hexagon bolt heads and nuts.
This invention is to be distinguished from implements which have a clamping action designed so that increasing effort applied to the handle of the implement causes increasingly tight clamping pressure in the jaws of the implement. This invention relates to ratchet action open ended spanners whose jaws can move from an open position to being locked in a closed position without exerting a clamping pressure on a bolt head or nut. The invention is thus not applicable to the turning of pipes or similar round objects but only to the turning of bolt heads and nuts.
2. Description of the Prior Art
Oil well tongs or wrenches can be perceived to have a structural resemblance to spanners of the type according to the present invention but the resemblance is superficial because these tongs or wrenches are so designed for the interaction of the handle, upper jaw and lower jaw to cause pressure on the handle to be transferred to a clamping pressure in the jaws. Thus, for example, "Oil well tongs or wrench" are described by J. S. Turner in U.S. Pat. No. 1,718,719 where the handle is pivoted on an upper jaw and a lower jaw is pivoted on the upper jaw, the handle having a nose extension beyond its pivot point which acts as a lever so that pressure on the handle transfers leverage to create a clamping pressure in between the jaw.
Similarly a "Wrench provided with cam actuated self tightening jaws" is described by R. L. Gregory in U.S. Pat. No. 2,441,144 where again a handle is pivoted to an upper jaw and a lower jaw is pivoted to the upper jaw but here the lower jaw has an extended heel extending away from the jaws to interact with a cam or lobe of the handle and the action is again such that increasing pressure on the handle is translated into increasing clamping pressure of the jaw.
Even the "non-slip ratcheting wrench having double hexagon spaced jaw face grooves" described by G. T. Logan in U.S. Pat. No. 2,618,996 although specifically described with reference to acting on a bolt head or nut has a structure which has the same action as the oil well tongs or wrench of J. S. Turner.
The "Open end ratcheting wrench" described by G. T. Logan in U.S. Pat. No. 2,537,838 also has jaws with indentations for a hexagon head bolt or nut but has an opposite action to the wrench in U.S. Pat. No. 2,618,996 in the sense that the nose extension of the handle opens the jaws rather than closing them. However, also U.S. Pat. No. 2,537,838 transfers increasing pressure on the handle to increase clamping force in the jaws.
By contrast the "Movable jaw wrench" described by A. A. Keranon in U.S. Pat. No. 3,044,335 has a mechanism which, according to the direction in which the handle is moved alternately locks the jaws in the position to fit the bolt head or nut or releases the jaws to open. In Keranon the upper jaw has a heel which projects in the opposite direction to the jaws from the hinge pin by which it is hinged to the handle and the opening or closing of the lower jaw with respect to the upper jaw is controlled by complex sliding surfaces and a movable segment.
Also the "Ratchet action open end wrenches" described by L. R. Dyck in U.S. Pat. No. 3,606,805 which also has an upper jaw pivoted to the handle and a lower jaw pivoted to the upper jaw has an arrangement where a lower jaw insert reacts with a nose portion of the handle which extends beyond the hinge pin connecting the upper jaw to the handle towards the jaw area to create a quasi lower jaw. This construction again does not convert pressure on the wrench handle into a clamping action at the jaws but merely provides for the alternate opening and closing of the jaws.
A further disadvantage of all of these designs, save for Gregory, is that it is deemed necessary to provide a spring which acts to tend to open the jaws which lessens the robustness and simplicity of the structure and thus reduces it reliability especially for long and heavy work in arduous conditions.